Myelodysplastic syndromes (MDS) are hematopoietic stem cell malignancies characterized by dysplastic and ineffective hematopoiesis. MDS bone marrow precursors have a larger cell size, deregulated proliferation and maturation, and accelerated attrition by programmed cell death.
Lenalidomide (Revlimid®, Celgene Corporation, NJ, USA) (LEN) was initially intended as a treatment for multiple myeloma, but has also shown efficacy in MDS. Lenalidomide has significantly improved overall survival in myeloma (which generally carries a poor prognosis). Lenalidomide is undergoing clinical trial as a treatment for Hodgkin's lymphoma, as well as non-Hodgkin's lymphoma, chronic lymphocytic leukemia and solid tumor cancers, such as carcinoma of the pancreas. Patients with an interstitial deletion of Chromosome 5q have a high rate of response to lenalidomide, but most MDS patients lack this deletion. Approximately 25% of patients without 5q deletions also benefit from lenalidomide therapy, but response in these patients is difficult to predict. In addition, treatment with erythropoietin (EPO) may improve anemia in about 15-20% of patients with MDS. However, methods are needed to predict this responsiveness.